1. Field of the Invention
Embodiments of the present invention relate to techniques for improving the vibrational health of computer systems. More specifically, the present invention relates to a method and an apparatus that actively cancels vibrations that affect the performance of components, such as hard disk drives (HDDs), within a computer system.
2. Related Art
Computer systems such as servers and storage arrays can be adversely affected by mechanical vibrations that affect internal computer system components and structures. In particular, when structural resonances are present in servers or storage arrays at some characteristic frequencies, it is possible that cooling fans or disk drives operate at rotational frequencies that are substantially the same as one of the structural resonant frequencies. When this condition occurs, the rotational motions of the fans or the disk drives can excite a structural resonance within the computer system's mechanical structure, thereby causing destructive amplification of internal vibrations. The amplified internal vibrations can subsequently lead to degradation of throughput associated with hard disk drives (HDDs), and can also accelerate other mechanical failure mechanisms.
Note that the above-described vibrational problems are becoming more significant because of the following trends in computer system manufacturing: (1) cooling fans are becoming increasingly more powerful; (2) chassis and support structures are becoming weaker because of design modifications that reduce cost and weight; and (3) internal disk drives, power supplies, and other system components are becoming more sensitive to vibration-induced degradation.
At the same time, HDDs are becoming more sensitive to vibrations because the storage density for HDDs has increased to the point where a write head has to align with a track which is less than 20 nanometers wide. Moreover, the write head floats only 7 nanometers above the disk surface. These extremely small dimensions make the read and write performance of the HDDs extremely sensitive to vibrations. Even low levels of sustained vibrations can significantly deteriorate I/O performance of the HDDs.
A “brute force” approach to decouple externally generated vibrations from the HDDs involves: (1) identifying HDDs which are adversely affected by the vibrations; (2) identifying the vibration sources; and (3) inserting rubber or foam dampers, grommets, or stiffeners in available spaces around identified vibration sources and vibration-sensitive HDDs in an effort to isolate these components from the rest of the computer system. However, using elastomeric dampers/stiffeners and grommets is undesirable because these materials are known to deteriorate with time. Moreover, the above-described approach can be very costly and inefficient in practice.
Hence, what is needed is a method and an apparatus that facilitates mitigating vibration problems for HDDs without the above-described problems.